In the manufacture of articles that comprise an opto-electronic semiconductor device (e.g., a LED or a PIN detector) it is frequently necessary to precisely position an end of an optical fiber relative to the device. For instance, if the device is a LED or a detector diode then it is frequently necessary to position a fiber end a predetermined distance above the device surface and centered with, respectively, the beam of radiation that is emitted by the LED, or the photosensitive region of the detector. The necessity can arise at many points during the manufacturing process, for instance, at a relatively early stage for, e.g., device testing purposes, or during relatively late assembly steps (e.g., when positioning and securing the end of a fiber "pigtail" relative to the device).
There are known techniques for centering the end of a length of fiber with the relevant portion of the device surface. For instance, software-controlled equipment for positioning the end of optical fiber relative to the beam of radiation emitted by an LED is available from Newport Corporation of Mountain View, Calif. While these techniques typically can satisfactorily automatically position the fiber end in the x-y plane (i.e., in the plane normal to the axis of the emitted beam), it has so far proven difficult to automatically precisely position the fiber end a small predetermined distance (e.g., 50 .mu.m) from the relevant device surface, and to consistently achieve this ".DELTA.z" adjustment without contacting the device surface with the fiber end.
Because of the referred-to difficulty the final .DELTA.z adjustment has, up to now, typically been made manually, by a trained operator using an optical microscope. This is obviously an expensive process step, and it would be highly desirable to have available an automatic technique for making the final .DELTA.z-adjustment. This application discloses such a technique, especially useful for devices wherein the relevant portion of the device surface is substantially flat.